X-Message-Number: 12634 From: Thomas Donaldson <> Subject: about how brains work Date: Tue, 26 Oct 1999 00:48:01 +1000 (EST) Hi everyone! While I hesitate to praise myself, I will point out that PERIASTRON has spent years discussing the different features of LTP and LTD, and how they act as the initial stages in formation of memories. Clearly how our brains work is important to any program to freeze or vitrify them so that they can be revived WITH MOST MEMORIES INTACT. Seriously, guys, if you don't study up on their background, these papers on LTP or the density of "information" in neurons (otherwise known as the density of synapses) are going to very easy to misunderstand. One major misunderstanding which apparently exists in several recent posts is that LTP or LTD are themselves the forms that long term memory takes. The problem with this is that once rats or other animals have been trained up, say, on a maze, then the experience of the maze will no longer produce LTP or LTD in any of their neurons. No, they haven't forgotten; it's just that both activities pertain only to the earlier stages of learning. The end result consists of a modification of the neuron's synapses, including sometimes the growth of new synapses, and with this the animal will automatically behave according to its past learning. I will provide lots of references to anyone who is interested. But most of all, I took up that subject of memory and how it worked precisely because it was the one feature which we want to preserve but did not know how to do that preservation. (All else can be done by cloning or other such methods). And over the last 15 years there's been lots of progress in understanding how brains work. No, we're not yet at a time in which all pertinent questions have been answered, but many have and we have a better understanding than we used to. I'll also point out (to those who are so fond of returning, somehow, as computers) that if you want your return to be successful, you too should be interested in how your brain works, particularly for memory and your sense of identity (both of which are now researched by many neuro- scientists). If we don't know how brains work, we can hardly know how to resurrect you, even in a computer. (And even if you want to go on from there into a quite different form, you still have to START with your memories in a brainlike entity). Finally, although the kind of neural net very likely differs from any computer neural net yet devised, we consist of many interconnected neural nets. And if you read about neural nets you'll find interesting things --- particularly those which, like our brains, can learn without explicitly being told. One interesting fact is that reading the content of a neural net's memories into a binary scheme of bits isn't at all trivial. Yes, in at least one special case it's made easy by the specific structure of the neural net (each "neuron" gets 2 inputs, which only take ON or OFF. It then passes the combined result to another "neuron"). But it's quite clear that our brains are not built that way... most computer neural nets, even, aren't built that way. Best wishes and long long life to all, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=12634